Preparation And Properties Of Biomedical Lubricants And Surface Lubrication Coatings

In this paper,the lubrication mechanism of synovial joints in natural animals is reviewed firstly.It is pointed out that the key mechanism of joint superlubrication lies in the hierarchical brush structure formed by the synergistic interaction between glycoprotein and hyaluronic acid.The assembly can be dispersed into joint synovial fluid or assembled on cartilage surface to achieve high lubrication performance.Chitosan and poly(amino acid)are natural biological macromolecules,while biomimetic dopamine groups of mussels can adhere to different materials.In this thesis,on one hand,we designed and prepared chitosan graft poly(amino acid)copolymer to mimic the glycoprotein lubricants in nature.On the other hand,mussel inspired one-step fabrication of low friction and antifouling coating was also developed for biomedical applications.1)Good biocompatibility is the key to the biological materials.In order to mimic the glycoprotein lubricants in synovial joints,we synthesize chitosan-g-poly(amino acid)copolymer by combining the completely biocompatible chitosan and poly(amino acid).N-carboxylic anhydride of L-glutamic acid benzyl ester(NCA monomer),was prepared firstly.Then,chitosan-g-poly(amino acid)copolymer was prepared by in situ ring-opening polymerization of NCA monomers initiated by amino groups on modified chitosan.After hydrolysis under acidic conditions,the water-soluble chitosan-g-poly(amino acid)copolymer was obtained.It can be fully dissolved in water and used as biological lubricant.The brush like copolymer solution showed good affinity to titanium alloy substrate and can effectively improve the lubrication of titanium alloy surface by interface adsorption and hydrodynamic effect.In view of the good biocompatibility and efficient lubrication,chitosan-g-poly(amino acid)copolymer will find widespread applications in biomedical areas,such as artificial joints.2)Ultra-lubricating and antifouling polymer coating materials play a very important role in reducing the friction between the bio-implant and human tissue interface and reducing the pain in the use process.However,the preparation methods of low-friction coating are generally complex.In this part,a one-step method for preparing super-lubricating and antifouling polymer nano-coatings based on dopamine self-polymerization was developed.During the preparation of the coatings,dopamine molecules self-polymerized to form polydopamine(PDA)adhesion layer,and dopamine can initiate in-situ polymerization of acrylic monomers to form low friction polymer chains in the process of self-polymerization.This method skillfully avoided complex synthesis of energetic polymers.The prepared PDA-PSBMA amphoteric polymer coatings exhibit excellent lubrication and antifouling properties.The friction coefficient of the coatings in pure water and PBS buffer solution is as low as 0.004,and the coatings can maintain good lubrication performance in biological media.The method is simple to operate and has good universality.It can be applied to the surfaces of various inert biomaterials(Ti₆AI₄V,glass,PDMS,PS,PMMA,etc)and medical catheters.Different types of ultra-low friction and antifouling lubrication coatings have been prepared directly.